javascript动画算法实例分析

时间:2021-1-8 作者:admin

本文实例讲述了javascript动画算法。分享给大家供大家参考。具体如下:

动画算法

Linear:无缓动效果(匀速运动);
Quadratic:二次方的缓动;
Cubic:三次方的缓动
Quartic:四次方的缓动;
Quintic:五次方的缓动;
Sinusoidal:正弦曲线的缓动;
Exponential:指数曲线的缓动;
Circular:圆形曲线的缓动;
Elastic:指数衰减的正弦曲线缓动;
Back:超过范围的三次方缓动);
Bounce:指数衰减的反弹缓动。

每个效果都分三个缓动方式(方法),分别是:

easeIn:从0开始加速的运动;
easeOut:减速到0的运动;
easeInOut:前半段从0开始加速,后半段减速到0的运动。

函数的四个参数分别代表:

t— current time(当前时间);
b— beginning value(初始值);
c— change in value(变化量);
d—duration(持续时间)

运算的结果就是当前的运动路程。

Tween.js如下:

Tween = { 
 Linear: function(t,b,c,d){ return c*t/d + b; },
 Quad: {
  easeIn: function(t,b,c,d){
   return c*(t/=d)*t + b;
  },
  easeOut: function(t,b,c,d){
   return -c *(t/=d)*(t-2) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2*t*t + b;
   return -c/2 * ((--t)*(t-2) - 1) + b;
  }
 },
 Cubic: {
  easeIn: function(t,b,c,d){
   return c*(t/=d)*t*t + b;
  },
  easeOut: function(t,b,c,d){
   return c*((t=t/d-1)*t*t + 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2*t*t*t + b;
   return c/2*((t-=2)*t*t + 2) + b;
  }
 },
 Quart: {
  easeIn: function(t,b,c,d){
   return c*(t/=d)*t*t*t + b;
  },
  easeOut: function(t,b,c,d){
   return -c * ((t=t/d-1)*t*t*t - 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2*t*t*t*t + b;
   return -c/2 * ((t-=2)*t*t*t - 2) + b;
  }
 },
 Quint: {
  easeIn: function(t,b,c,d){
   return c*(t/=d)*t*t*t*t + b;
  },
  easeOut: function(t,b,c,d){
   return c*((t=t/d-1)*t*t*t*t + 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
   return c/2*((t-=2)*t*t*t*t + 2) + b;
  }
 },
 Sine: {
  easeIn: function(t,b,c,d){
   return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
  },
  easeOut: function(t,b,c,d){
   return c * Math.sin(t/d * (Math.PI/2)) + b;
  },
  easeInOut: function(t,b,c,d){
   return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
  }
 },
 Expo: {
  easeIn: function(t,b,c,d){
   return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
  },
  easeOut: function(t,b,c,d){
   return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if (t==0) return b;
   if (t==d) return b+c;
   if ((t/=d/2) < 1) return c/2 * Math.pow(2, 10 * (t - 1)) + b;
   return c/2 * (-Math.pow(2, -10 * --t) + 2) + b;
  }
 },
 Circ: {
  easeIn: function(t,b,c,d){
   return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
  },
  easeOut: function(t,b,c,d){
   return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
   return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
  }
 },
 Elastic: {
  easeIn: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d*.3;
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2*Math.PI) * Math.asin (c/a);
   return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
  },
  easeOut: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d*.3;
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2*Math.PI) * Math.asin (c/a);
   return (a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b);
  },
  easeInOut: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d/2)==2) return b+c; if (!p) p=d*(.3*1.5);
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2*Math.PI) * Math.asin (c/a);
   if (t < 1) return -.5*(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
   return a*Math.pow(2,-10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )*.5 + c + b;
  }
 },
 Back: {
  easeIn: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158;
   return c*(t/=d)*t*((s+1)*t - s) + b;
  },
  easeOut: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158;
   return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
  },
  easeInOut: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158; 
   if ((t/=d/2) < 1) return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
   return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
  }
 },
 Bounce: {
  easeIn: function(t,b,c,d){
   return c - Tween.Bounce.easeOut(d-t, 0, c, d) + b;
  },
  easeOut: function(t,b,c,d){
   if ((t/=d) < (1/2.75)) {
    return c*(7.5625*t*t) + b;
   } else if (t < (2/2.75)) {
    return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
   } else if (t < (2.5/2.75)) {
    return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
   } else {
    return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
   }
  },
  easeInOut: function(t,b,c,d){
   if (t < d/2) return Tween.Bounce.easeIn(t*2, 0, c, d) * .5 + b;
   else return Tween.Bounce.easeOut(t*2-d, 0, c, d) * .5 + c*.5 + b;
  }
 }
}
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